[POWERPC] Donate idle CPU cycles on dedicated partitions

A Power6 can give up CPU cycles on a dedicated CPU (as opposed to a
shared CPU) to other shared processors if the administrator asks for it
(via the HMC).

This enables that to work properly on P6.

This just involves setting a bit in the CAS structure as well as the
VPA.  To donate cycles, a CPU has to have all SMT threads idle and
have the donate bit set in the VPA.  Then call H_CEDE.

The reason why shared processors just aren't used is because dedicated
CPUs are guaranteed an actual processor, yet the system is still able to
increase the capacity of the shared CPU pool.

Also rename the VPA's cpuctls_task_attrs field to a more accurate name.

Signed-off-by: Jake Moilanen <moilanen@austin.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 3 insertions, 1 deletions

diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c
index d6047c441034..a1d582e38627 100644
--- a/arch/powerpc/kernel/prom_init.c
+++ b/arch/powerpc/kernel/prom_init.c
@@ -635,6 +635,7 @@ static void __init early_cmdline_parse(void)
 /* ibm,dynamic-reconfiguration-memory property supported */
 #define OV5_DRCONF_MEMORY       0x20
 #define OV5_LARGE_PAGES         0x10    /* large pages supported */
+#define OV5_DONATE_DEDICATE_CPU 0x02    /* donate dedicated CPU support */
 /* PCIe/MSI support.  Without MSI full PCIe is not supported */
 #ifdef CONFIG_PCI_MSI
 #define OV5_MSI                 0x01    /* PCIe/MSI support */
@@ -685,7 +686,8 @@ static unsigned char ibm_architecture_vec[] = {
         /* option vector 5: PAPR/OF options */
         3 - 2,                          /* length */
         0,                              /* don't ignore, don't halt */
-        OV5_LPAR | OV5_SPLPAR | OV5_LARGE_PAGES | OV5_DRCONF_MEMORY | OV5_MSI,
+        OV5_LPAR | OV5_SPLPAR | OV5_LARGE_PAGES | OV5_DRCONF_MEMORY |
+        OV5_DONATE_DEDICATE_CPU | OV5_MSI,
 };
 
 /* Old method - ELF header with PT_NOTE sections */